Cordless switchboard



All@ 20, 1963 E. l. ENGQvlsT ETAL 3,101,395

CORDLESS SWITCHBOARD 3 Sheets-Sheet 1 Filed May 14, 1959 p LTL L mw.

Aug- 20, 1963 E. |.ENGQv1s-r ETAL 3,101,395

CORDLESS SWITCHBOARD 3 Sheets-Sheet 2 Filed May 14, 1959 /QrroR/VE ys Aug. 20, 19-63 E. l. ENGQvlsT ETAL. 3,101,395

CORDLESS SWITCHBOARD v Filed May 14, 1959 3 Sheets-Sheet 3 Fig. 3

/Qrro 1PA/E YS United States Patent 3,101,395 CQRDLESS SWITCEBUARD Erik Isidor Engqvist, Hagersten, and .lohn Helge Willy Adenstedt, .lohanneshorg Sweden, assignors to Telephonaktiebolaget L M Ericsson, Stockholm, Sweden, a

corporation of Sweden Filed May 14, 1959, Ser. No. 813,178 Claims priority, application Sweden May 23, 1958 4 Claims. (Cl. 179-99) The present invention refers to `a cordless switchboard, ie. a switchboard, at which all the connect-ions between the extensions connected to the switchboard are established by the operation of push buttons or keys only. In such switchboards a `group of keys is provided for such extension and these groups yare for the sake of clearness yarranged in parallel rows. Within the 'different rows corresponding keys have the same function so that, provided a certain key inone row in operated position connects a cord circuit to an extension assigned to this row, a corresponding key of another row in operated position connects the same cord circuit to the extension of this latter row. r[he two extensions are thus communicated when both keys simultaneously are operated.

Incoming exchange lines may be terminated in similar key rows as used for the extensions, whereby connections to these lines are efectuated by means of normal cord circuits, or these exchange lines may be connected to special cord circuits, which in this case are not to be used for interconnecting the extensions.

Because of the large number of contact means, ire. keys or push buttons, each of which is provided with a plurality of contact springs, the wiring of these switchboards is rather complicated and the switchboards are expensive.

Because of the mounting of a plurality of push buttons or keys of the conventional design in rows as indicated above, the accessibility for maintenance work is rather bad. In order to adjust the contact springs of a key, the vkey has [to be detached in order to make the springs accessible, whereby the risk `arises of breaking wires connected to the key.

One object of the invention is to provide Ia simple cord less switchboard in which each contact means includes only a yfew contact springs and 4in which the wiring is reduced as far as possible.

Another Iobject is to provide a switchboard in which the contact springs are easily accessible `for adjustment without having to -detach the contact means.

An additional object of the invention is to provide la switchboard having an extremely simple operators switching procedure.

This is achieved principally by the fact that the contact means are resilient, and that each group of contact means, arranged for connecting the necessary auxiliary circuits, such as cord circuits, operators circuit etc., to an extension, is provided with a mechanical Ablock-ing member, which is yieldably held in a blocking position 'where it retains any contact means yof the group brought to active position, said blocking member at operation of any other contact means of the group being momentarily removed from the blocking position, soi that the contact means, retained up to that moment, is liberated and by its resiliency brought back to inactive position.

The invention will be further' described by means of an embodiment with reference to the accompanying drawings, in which:

FIIG. 1 is a schematic representation of the contact arrangement of the switchboard, including two vertical pushbutton strips with locking b-ars, joined together by horizontal contact-carrying plates;

FIG. 2 is ya diagram showing the principal electrical circuits of the switchboard in a preferred layout, all the 3,l0|l,395 Patented Aug. 20, 1963 f'ce contacts lof each extension line circuit being connected in series; and

FIG. 3 is a diagram showing the circuit of ian extension line in `an alternative design of the switchboard, all the contacts of the extension line circuit being connected in parallel.

Thek contact means are larranged in 'a supporting iirame consisting on the one hand of Ia number of plane, parallel land equidistant push button strips 11 and on the other hand of contact plates 12 of insulating material that are placed at right angles 'to the strips and are also parallel )and equidistant.

Eachr push button strip carries along the one edge a number of push buttons -13 which are normally kept in inactive position away from Ithe edge by means of individual springs (not shown on the ligure) yand that may be ldepressed against the spring fonce into a position, where the contact springs are actuated.

The push button endstur-ned inwards the strip are designed as two parallel bars 14 and 15, that are placed on each side of the strip, the bars being formed for actuating each a pair of contact springs.

A blocking bar 16 common to lall of the push buttons, is in a convenient way provided on the strip, which bar by means ot a spring (not shown) is held in a blocking position, in which any 'depressed button is retained. The blocking bar is in the known way so |arranged that it is momentarily removed from the blocking position, when 'any push button is depressed, rwhereby any button, retained up to that moment, is liberated, so that the same by the force of its spring is returned to inactive position.

The :contact plates .carry iixed contact bars 17 and movable contact springs 18, that can be actuated by the push buttons. Two contact bars are xed in parallel relationship' on each side of the plate adjacent tot one olf the longitudinal .edges of the plate. The movable contact springs are of equal size, 'are fixed to the opposite longitudinal `|edge, of the plate and are each designed with two legs of equal size, the legs being placed symmetrically on `each side of the plate. The edge carrying the contact springs is provided -with recesses tor said springs, of which recesses every second 19 is of 'a certain depth while the others 2i) are of a different depth. The difference of depth corresponds to the distance between the con-tact bars, so that the legs of the contact springsy on each one side of the contact plate with `their ends reach alternatively tol the one cont-act bar and to the other.

ln order to facili-tate assembling of the strips and plates to a frame both are provided with slits 21 and 22. On the strips the width of the slits 21 equals the thickness of the contact plates, the width of the slits 22 of the plate equalling the thickness of the contact strip. The lengths of the slits as well as their location along the strip and the plate respectively are chosen in such a way that when assembling the strips and plates that their respective slit bottoms touch each other, and the inner endsy of the push buttons are brought to an adequate position for co-operation with the contact springs. Furthermore the contact springs of the different contact plates, each one with its legs, are in Contact with equally placed contact springs on adjacent plates. -In this way an electrical circuit is formed, on either side ofkeach push button strip, by series connected contact springs from the uppermost to the lowermost contact plate of the ligure. The inner ends of the push buttons are located on each side of the strip, each one between two contact springs Ithat rest against each other. 'Ilhe push buttons, however, in their inactive position do not touch the springs. W'hen a button is pressed, both the circuits are interrupted and the contact springs brought in contact with contact bars on the ad- .jacent plates.

FIG. 2 shows a simplified diagram of `the switchboard. For the salie of simplicity only equipment for two extensions, one cord circuit and one exchange line, is shown on the drawing, whereas only those parts of the operators circuit that are necessary for explaining the principle of the invention are shown.

The switchboard is provided with one push button strip for each extension and with one for the operators circuit, the diagram of the gure including four push buttons TT, TS, TC and TA for each push bntton strip. At `the push button strips provided for the extensions, La and Lb indicate the connection points of the aand b-wire of the extension. B is an indicator that serves as a signal means for calling and conclusion signals.

By means of the button 'IT the extension line can be connected to the operators circuit, by means of the TS- button lto a cord circuit, by means of the TC-button -to the exchange line and by means of the 'TA-button to the v signal indicator. Each push button actuates two contact spring pairs 2, 3 and 6, 7, all the contact spring pairs indicated by 2, 3 being located on one side of the strip while the contact pairs 6, '7 are on the other side.

With 1, 6l, 5 and 3 are indicated the xed contacts of each push button, which contacts in FIGURE 1 are represented bythe xed contact bars 17 of the contact plates.

The common equipment of the switchboard, such kas ringing circuit and the operators equipment, is not shown in the gure, as this would be an unnecessary complication of the gure. Within the dashed square O is only shown a change relay TR, while equipment of known diagrammatical design is excluded. FR indicates a feeding relay of the cord circuit, CL are connection points for an exchange line and CI a call indicator of said line. The call indicator `Cl is connected in series with a condenser Cl, which can be short-circuited by means of a manually operable push button V. DR is a holding coil for the exchange line and CRll is an auxiliary relay for connecting the holding coil. CR is a supervisory relay that in order not to introduce an unnecessary attenuation in the exchange line is bridged by a condenser C2.

rllhe functioning of :the switchboard will be understood from the following description.

Internal Calls When an extension is disengaged, the 'TA-button of this extension is depressed, and when the handset of the extension is lifted, a circuit is closed from positive on the button TA through contacts 3, 4, 8 and 7 of the same, line La, extension instrument, line Lb, contacts 6, 7 of buttons TT, TS and TC, contacts 6, 5, ll, 2 of TA, contacts 3, 2 of the buttons TC, TS and TT through the winding of the indicator B tto negative. The indicator B signals a call and for answering this call the operator presses the TT-button of this extension, whereby the TA-button is released. The contacts 3 and 2 of the 'TA-button are thereby closed and a circuit is formed from positive on TA through contacts 3, 2 of TA, TC and TS and contacts 3, 4 of TT to relay TR and negative, whereby said relay operates and connects the operators circuits to the contacts 5 and S of the button TT. Through the contacts 5 and 6 of the button TT of the extension the b-wire of this extension is connected to the operators circuit while the a-wire is connected through the contacts '7, 8 of the same button TT and contacts 6, 7 of TS, TC and TA. If the calling subscriber solicits a connection to another extension and this extension is disengaged, the operator presses a TS-button belonging to this extension and corresponding to a free cord circuit, whereby the TT-button of this extension is restored. Thereafter she presses the 'IT-button of the solicited extension, whereby lthis extension is connected to .the operators circuit. After having sent out a ringing signal, which is eiected by a ringing button (not shown) of the operators circuit, she oppresses the TS-button of the called extension, whereby the two extensions are connected together through contacts i 5, 6 and 7, 8 of their respective TS-buttons. The feeding relay FR, that is connected -to the contacts 5 and 8 of these buttons, is common to the two extensions. The relay was operated through the loop of the calling subscriber, when the 'TS-button of this extension was oppressed, and is maintained operated until, ater conversation, the two subscribers have hung up their receivers. This having occurred the relay FR releases and connects current through its contact to the contacts ll and 2 of the two TS-buttons land from these through the contacts 3 and 2 of the respective rIT-buttons to the indicators B of both extensions, which are actuated and show conclusion signals. The operator oppresses the 'IA-buttons of the two extensions, whereby the TS-buttons are released and their contacts i, 2 interrupt the circuits to the indicators. The equipments of the extensions are thereby immediately ready for new calls.

Outgoing Exchange Calls if the calling extension asks for an exchange line, the operator presses a 'TC-button of this extension correspending to a free exchange line, whereby the extension through contacts 5, 6 and 7, 8 respectively of this button is connected to the exchange line (CL). The extension receives feeding current from the exchange and, if the same is an automatic exchange, the number can be dialed by means of the extension dial. The relay CR that is intercalated in the loop, operates by the feeding current and is maintained operated during the call. When the extension restores vthe receiver, the circuit is interrupted in the instrument of the extension and the relay CR releases. `Current is then connected from the contacts of the relay through contacts 1, 2 of the lCR-buttort to the indicator of the extension, which shows conclusion signal. The operator then presses the TA-button, whereby the rIC-button is restored yand the exchange connection disconnected.

IncOming Exchange Calls At a call on :an exchange Iline the call indicator CI is actuated. The operator connects herself to the exchange line by pressing the TC-button of the operators circuit. When the calling subscriber solicits connection with a determined extension, the operator sends a yringing sign-al to this extension in the same way as indicated Ibelow internal Calls and thereafter she presses the TC-button oi said extension. Thereby a circuit is closed lfrom positive on the contacts 3, 2 of the TA-button of the exchange, through contacts 3, i of Ithe 'TC-button, the Winding of relay RCL the contacts l, Z of the TC-button of the operator, contacts 3, 2 of the TS- and "IT-buttons to negative. Relay RCll operates and takes hoilding to negative on its own contact. By means of another make contact on CRIL the holding coil DR is lsimultaneously connected across the exchange line, whereby this line is retained until the extension answers, so that the operator in the meantime is at liberty to handle other calls. When the extension answers, the supervisory yrelay CR operates and when this relay after termination of the call releases, current is connected t-o the indicator of the extension, which shows conclusion signal as described below outgoing exchange calls. The operator then presses the rlTA-button of the extension, whereby the TC-button is liberated. The relay CRl releases and the extension as well as `exchange line are free ttor new calls. ylif the extension asked for by the calling subscriber is busy and the subscriber desires to wait until it becomes disengaged, the operator presses the ybutton V, thereby short-circuiting the condenser Ci. 'llhe Ifeeding current from theexchange thereby actuates the call indicator Cl, that consequently shows a calling signal, so that the operator is reminded that the subscriber is waiting on the line.

The invention is of course not limited to the example of embodiment described, several modifications lbeing possible without changing the scope of the invention. Thus it is not necessary, that the contact pairs, provided lfor connecting the extension to different auxiliary circuits, are connected in series; they may also be connected in parallel. FIG. 3 shows a diagram'rfor 1an extension equipment in which the contact pairs referred to are connected in parallel.

We claim:

f1. A cordless manual switchboard 'for connecting local lines to trunk lines and local lines in pairs comprising, calling signal means for each local line, la plurality of push buttons for each local line, locking means releasably securing a single one of said push buttons in a depressed position and simultaneously releasinganother depress-ed push 'button in response to manual yactuation thereof, said one of said push buttons in ysaid depressed position connecting said calling signal means to the respective local line.

2. A cordless manual switchboard as set forth in claim 1, further comprising a push button strip ffor each local line land a plurality of contact strips extending past all off the push :but-ton stri-ps at righ-t angles thereto, each contact strip carrying on either side at least one longitudinal contact bar and :at least one movable contact spring for each push button strip, each said movable contact spring being responsive to each responsive push lblutton and displaceable in response to actuation of said push button into contact with said contact bar.

3. A cordless manual switchboard as set forth in claim 2, wherein said contact strip comprises ian oblong plate of dielectric material, at least one two-legged contact spring for each push button strip carried by said plate /with one leg on each side of said plate, and each leg .being -actuatable Aby lan adjacent push button.

4. A Icordless manual switchboard as set riorth in claim 3, wherein each movable leg of each contact spring in a normally inactive position is in contact with a leg of la contact spring located on an 'adjacent contact strip, whereby said'contact springs compose a series circuit along each l push Ibfutton strip from a contact spring on the uppermost contact strip to a conta-ct spring lon the lowermost contact strip through contact springs on intermediate 'contact strips.v

References Cited inthe le of this patent UNITED STATES PATENTS 2,107,158 vLewis Feb. 1, 1938 2,559,561 Micha July 3, 1951 2,613,281 Micha Oct. 7, 1952 

1. A CORDLESS MANUAL SWITCHBOARD FOR CONNECTING LOCAL LINES TO TRUNK LINES AND LOCAL LINES IN PAIRS COMPRISING CALLING SIGNAL MEANS FOR EACH LOCAL LINE, A PLURALITY OF PUSH BUTTONS FOR EACH LOCAL LINE, LOCKING MEANS RELEASABLY SECURING A SINGLE ONE OF SAID PUSH BUTTONS IN A DEPRESSED POSITION AND SIMULTANEOUSLY RELEASING ANOTHER DEPRESSED PUSH BUTTON IN RESPONSE TO MANUAL ACTUATION THEREOF, SAID ONE OF SAID PUSH BUTTONS IN SAID DEPRESSED POSITION CONNECTING SAID CALLING SIGNAL MEANS TO THE RESPECTIVE LOCAL LINE. 